Background of the Invention
The dental profession, since the advent of tooth repair, has sought out materials and devices which were pliable, yet strong enough to withstand the several thousand pounds per square inch bite pressures which are capable of being experienced.
Depending on the degree of permanency needed, a variety of materials have been used, ranging from gold, at one end of the spectrum, to a wide range of plastics at the other end. Temporary crowns may even be aluminum, or aluminum alloys of various compositions.
In most instances, the process of fitting a patient with a custom crown begins with the preparation of the tooth, after which an impression is made, from which a crown is fashioned. Then the patient returns for the cementation of the crown, a second visit. In working with children, a one visit procedure is now possible by using a preformed crown, and that is an obvious great advantage, in that it engenders greater cooperation from an ever reticent, and often downright frightened child. The parent is delighted to have to pay for only one visit.
A preformed resin crown, as an aesthetic alternative to stainless steel crowns, have been used with varying degrees of success for some years. Failures have mainly been due from over preparation of teeth to compensate for the bulkiness, indigenous to previous plastic crowns. Other failures have been attributed to such crowns literally falling off due to the lack of satisfactory luting agent, or splitting due to internal stress caused from deformation.
Crown forms, used to fashion the crown itself, resemble a crown, but are typically very thin (0.006 inches) in wall thickness, and are intended to be discarded after use. To date, there has been little, if any, effort to amalgamate the technology of crowns and crown forms to achieve a dual function appliance.